1. Field of the Invention
The present invention relates to a hard disk drive unit and a method of manufacturing the drive unit.
2. Description of the Prior Art
A hard disk drive unit is provided with: a motor mounted on a base member of a housing; and a swing arm (i.e., head arm) which is provided with a magnetic head in its front-end portion. By means of the magnetic head, data is stored in a magnetic disk and retrieved from an arbitrary position of the magnetic disk. On the other hand, hitherto, the base member of the housing of the hard disk drive unit is manufactured by using a casting process or a press working. A casting product 11 of the base member shown in FIG. 7 is manufactured by using a casting process as follows:
(1) an aluminum base member is manufactured by using a die-casting process; PA1 (2) then, gases such as air and the like confined within cavities, stains such as rust and like foreign matters are removed from the base member, the gases being fatal to the hard disk in performance; PA1 (3) further, in order to keep the surface of the base member clean, the surface of the base member is treated with suitable chemicals and/or painted, i.e., coated with suitable films; PA1 (4) the thus treated base member is then machined to be precisely dimensioned; and PA1 (5) finally, the thus machined base member is washed out stains to keep itself clean. PA1 (a) the number of the necessary steps of the casting process is too large; PA1 (b) it is necessary to take measures to prevent the cavities from being formed in the casting process; PA1 (c) when the cavities are formed, it is very difficult to completely remove the stains such as oils and the like from the cavities, and, therefore very difficult to keep the base member clean, which makes it necessary to close the cavities in the base member with suitable coatings, or to treat the surface of the base member with suitable chemicals so as to clean the surface and prevent the rust from being produced in the surface; PA1 (d) metallic molds required in the casing process are very expensive; and PA1 (e) this increases the manufacturing cost of the base member. PA1 (a) although the frame 13 member is a sheet metal pressing, the number of press working steps for manufacturing the frame member 13 is too large since the frame member 13 is very complex in configuration; PA1 (b) an additional step for fixedly mounting the frame member 13 on the base plate 12 is required, in which additional step the frame member 13 must be strictly controlled in mounting position and mounting strength; and PA1 (c) this increases the manufacturing cost of a subassembly 12, 13 thus constructed of the base plate 12 and the frame member 13. PA1 a base plate, which assumes a predetermined shape in cross-section so as to form a pair of frame portions in its opposite sides, is made of metal, formed by using an extrusion process, and provided with a concave portion with a central hole through which a motor is mounted on the base plate and a mounting hole through which a swing arm is mounted on the base plate; PA1 the motor, which is provided with a spindle and has the spindle mounted in the central hole of the concave portion of the base plate in an insertion manner; and PA1 the swing arm, which has its base portion pivotally supported by a pivot through a bearing, the pivot being mounted on the base plate through the mounting hole. PA1 forcing a billet through a die to produce an elongated extruded product having a predetermined cross-sectional shape provided with a pair of frame portions in its opposite sides; PA1 cutting the extruded product to form a half-finished product having a predetermined length; PA1 forming the half-finished product into a base plate by subjecting the half-finished product to a press working, the base plate being provided with a concave portion and a hole; PA1 mounting a magnetic disk drive motor in the concave portion of the base plate; and PA1 mounting a pivot in the hole of the base plate, the pivot supporting a bearing through which a base portion of a swing arm is pivotally supported.
However, the above-mentioned casting process of the base member is disadvantageous in that:
In case of the press working, as shown in FIG. 8, an aluminum base plate 12 is subjected to the press working to form a concave portion 14 and a plurality of holes 15 therein. Then, a frame member 13, which is a sheet metal pressing, is fixedly mounted on each of opposite sides of the base plate 12.
The above-mentioned press working is free from the cavity problem inherent in the casing process, and, therefore advantageous in keeping the surface of the base member clean. However, the press working suffers from the following problems: